Uptake, Translocation, and Terminal Residue of Chlorantraniliprole and Difenoconazole in Rice: Effect of the Mixed-Application with Adjuvant

Comprehensive Study on the Effects of Peanut Leaf Characteristics and Tank-Mix Adjuvant on Droplet-Spreading Behavior

In agricultural production, the application of pesticides via spraying is an effective approach to controlling pests and diseases. However, the pesticide utilization efficiency in peanut fields is generally low, owing to factors such as crop-specific characteristics and the nonoptimal use of adjuvants. To enhance the spreading performance of droplets on the surface of peanut leaves and increasing pesticide utilization efficiency, in this study, the effects of leaf surface characteristics and three different types of tank-mixed adjuvants on the droplet-spreading characteristics of peanut leaves were comprehensively analyzed. The results indicate that structural differences exist between the adaxial and abaxial surfaces of peanut leaves, leading to varying degrees of hydrophobicity. The adaxial surface is covered with a uniform, erect, waxy crystal structure, which increases the surface roughness and consequently enhances hydrophobicity. On the Adaxial of peanut leaves have higher CA and lower SA. While tank-mix adjuvants can improve the wetting and spreading performance of droplets on peanut leaves, the efficacy of the methylated plant oil adjuvant Beidatong (BDT) and the mineral oil adjuvant VELEZIA PRO (VP) is limited. In contrast, organosilicon adjuvant Nongjianfei (NJF) effectively improved the wettability of peanut leaf surfaces. Specifically, the addition of NJF can significantly reduce the surface tension of the spray solution, dissolve the waxy structure on the surface of peanut leaves, and greatly enhance the spreading performance of droplets on those leaves. On the adaxial leaf surface, the contact angle (CA) of the droplet rapidly reached 0°, and the droplet-spreading area (SA) increased by 150 times. On the abaxial leaf surface, the effect of NJF was relatively weaker, where the CA was 16.5° and the SA increased by 3.8 times. Therefore, in peanut field applications, incorporating the tank-mix adjuvant NJF can greatly enhance the spreading and retention of pesticides on peanut leaf surfaces, thereby improving pesticide utilization efficiency.

Strategy for the Selection of Tank-Mix Adjuvants to Improve the Wettability of Unmanned Aerial Vehicle-Sprayed Liquids on Citrus Leaf Surfaces

The past decade has witnessed a growth spurt in aerial pesticide application by plant protection unmanned aerial vehicles (UAVs). However, compared to the traditional ground application, their operation characteristics of low capacity and high concentration put forward rather higher requirements for the wettability of pesticide solutions on the target crop surface, which was a critical link to the pesticide efficiency. Tank mix of adjuvants is a common measure to modify the spray liquid wettability during foliar pesticide application. Yet, given the wide variety of spray adjuvants available, how to select suitable ones based on crop leaf surface characteristics during pesticide application of plant-protection UAVs still lacks attention, especially for tree crops like citrus. Herein, the surface free energy of citrus leaf, the surface tension of tested liquids, and their contact angles on citrus leaf were determined, and the quantitative relationship between the contact angle and the surface tension and its components, as well as the citrus leaf surface free energy and its components, was analyzed. The surface free energy of the adaxial and abaxial surface of citrus leaf was as low as 30.31 mJ m-2 and 27.50 mJ m-2, respectively, showing that citrus leaves are relatively difficult to wet. However, addition with 1% (v/v) of the three tested spray adjuvants to the liquid significantly reduced the surface tension, especially the polar component, thereby substantially decreasing its contact angles on the citrus leaf surface. There was a significant positive correlation between the droplet contact angle on citrus leaf surfaces and liquid surface tension and its polar component, with total surface tension as the main variable and the polar component as the covariant. Our findings proposed a strategy for screening tank-mix adjuvants to improve spray liquid wettability on tree crop leaves during pesticide application by plant-protection UAVs.

Enhancing agrochemical delivery in citrus leaves with geraniol: a promising strategy for controlling huanglongbing (HLB)

BACKGROUND

Citrus huanglongbing (HLB) is a devastating disease in citrus, caused by Candidatus Liberibacter asiaticus (CLas), which primarily resides in the phloem where chemicals cannot effectively reach, posing a significant challenge in controlling HLB. To address these challenges, plant essential oils (EOs), widely used as transdermal enhancers and known for their benefits for plant tissues, were investigated for their potential to enhance chemical permeation.

RESULTS

In this study, seven EOs - eugenol, carvacrol, eucalyptol, geraniol, linalool, cinnamaldehyde, and d-limonene - were evaluated for their potential to enhance chemical penetration into citrus leaves. Preliminary screening with tracer methods revealed that geraniol provided the greatest enhancement of permeation, achieving the deepest and broadest distribution into the spongy tissue of the citrus leaf. The permeation levels of rhodamine B and crystal violet through the cuticular layer were elevated from 0.55 mg L-1 and 0.11 mg L-1 to 20.04 mg L-1 and 7.14 mg L-1, respectively, by the addition of geraniol. Further validation through high-performance liquid chromatography-mass spectrometry (HPLC-MS) confirmed that the penetration of fludioxonil and tetracycline into citrus leaf tissues was enhanced by 15.07-fold and 20.43-fold, respectively. In planta experiments confirmed that adding geraniol to tetracycline and oxytetracycline via foliar application eliminated CLas bacteria in HLB-affected citrus more efficiently than controls.

CONCLUSION

Our study underscores the potential of geraniol as an effective EO-based permeation enhancer for combating HLB. By significantly improving the delivery and efficacy of bactericidal treatments, geraniol offers a promising strategy for managing this catastrophic citrus disease, potentially transforming the approach to controlling HLB. © 2024 Society of Chemical Industry.

Assessing the impact of Chlorantraniliprole (CAP) pesticide stress on oilseed rape (Brassia campestris L.): Residue dynamics, enzyme activities, and metabolite profiling

This study investigates the effects of chlorantraniliprole (CAP) pesticide stress on oilseed rape through comprehensive pot experiments. Assessing CAP residue variations in soil and oilseed rape (Brassia campestris L.), enzyme activities (POD, CPR, GST), and differential metabolites, we unveil significant findings. The average CAP residue levels were 18.38-13.70 mg/kg in unplanted soil, 9.94-6.30 mg/kg in planted soil, and 0-4.18 mg/kg in oilseed rape samples, respectively. Soil microbial influences and systemic pesticide translocation into oilseed rape contribute to CAP residue variations. Under the influence of CAP stress, oilseed rape displays escalated enzyme activities (POD, CPR, GST) and manifests 57 differential metabolites. Among these, 32 demonstrate considerable downregulation, mainly impacting amino acids and phenolic compounds, while 25 exhibit noteworthy overexpression, primarily affecting flavonoid compounds. This impact extends to 24 metabolic pathways, notably influencing amide biosynthesis, as well as arginine and proline metabolism. These findings underscore the discernible effects of CAP pesticide stress on oilseed rape.

Integrative physiological, critical plant endogenous hormones, and transcriptomic analyses reveal the difenoconazole stress response mechanism in wheat (Triticum aestivum L.)

Difenoconazole (DFN) is widely utilized as a fungicide in wheat production. However, its accumulation in plant tissues has a profound impact on the physiological functions of wheat plants, thus severely threatening wheat growth and even jeopardizing human health. This study aims to comprehensively analyze the dynamic dissipation patterns of DFN, along with an investigation into the physiological, hormonal, and transcriptomic responses of wheat seedlings exposed to DFN. The results demonstrated that exposure of wheat roots to DFN (10 mg/kg in soil) led to a significant accumulation of DFN in wheat plants, with the DFN content in roots being notably higher than that in leaves. Accumulating DFN triggered an increase in reactive oxygen species content, malonaldehyde content, and antioxidant enzyme activities, while concurrently inhibiting photosynthesis. Transcriptome analysis further revealed that the number of differentially expressed genes was greater in roots compared with leaves under DFN stress. Key genes in roots and leaves that exhibited a positive response to DFN-induced stress were identified through weighted gene co-expression network analysis. Metabolic pathway analysis indicated that these key genes mainly encode proteins involved in glutathione metabolism, plant hormone signaling, amino acid metabolism, and detoxification/defense pathways. Further results indicated that abscisic acid and salicylic acid play vital roles in the detoxification of leaf and root DFN, respectively. In brief, the abovementioned findings contribute to a deeper understanding of the detrimental effects of DFN on wheat seedlings, while shedding light on the molecular mechanisms underlying the responses of wheat root and leaves to DFN exposure.

Low concentration chlorantraniliprole-promoted Ca2+ release drives a shift from autophagy to apoptosis in the silk gland of Bombyx mori

The novel pesticide chlorantraniliprole (CAP) is widely used for pest control in agriculture, and the safety for non-target organisms of trace residues in the environment has received widespread attention. In the present study, exposure to low concentrations of CAP resulted in abnormal silk gland development in the B. mori, and induced the release of intracellular Ca2+ in addition to the triggering of Ca2+-dependent gene transcription. Moreover, the CAP treatment group exhibited down-regulation of oxidative phosphorylation and antioxidant enzyme-related genes in the silk gland, resulting in peroxide accumulation. Furthermore, transcript levels of autophagy-related genes were significantly up-regulated and protein levels of LC3-I and LC3-II were up-regulated, indicating an increase in autophagy. The protein levels of ATG5 and NtATG5 were also significantly up-regulated. While the protein levels of caspase3 and active caspase3 were significantly up-regulated consistent with the transcript levels of key genes in the apoptotic signaling pathway, ultimately affecting silk protein synthesis. Overall, these findings indicate that low concentration CAP induced abnormal development in the silk gland of B. mori by causing intracellular Ca2+ overload, which inhibits oxidative phosphorylation pathway and the removal of reactive oxygen species, leading to a driving a shift from autophagy to apoptosis. The findings herein provided a basis for evaluating the safety of CAP environmental residues on non-target organisms.